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In: Mechanical Engineering

A house that is losing heat to the 100C outdoors at an average rate of 50,000...

A house that is losing heat to the 100C outdoors at an average rate of 50,000 kJ/h is maintained at 220C at all
times during a winter night for 10 h. The house is to be heated by 50 glass containers each containing 20 L
(1L=10-3 m3
) of water that is heated to 80oC during the day by a solar heater. A thermostat-controlled 15-kW
back-up electric resistance heater turns on whenever necessary to keep the house at 220C. Analyse and
determine the following:
i. If the average solar intensity is 650 W/m2

and the solar heater has an efficiency of 80%, calculate the

area of solar heater to heat 20L of water from 220C to 800C in 8 hours.
ii. How long did the electric heating system run at night?
iii. Keeping 2nd law of thermodynamics in mind, what is the maximum efficiency of the back-up heater?
iv. If the heat provided by the back-up heater is provided using Carnot heat pump, determine the
reduction in electricity consumption.

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Expert Solution

samet mamat answered 5 months ago
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